This invention relates generally to the field of medical instrumentation and more specifically to the automated detection of defects of the retina, the optic nerve, and the brain's visual pathways.
A large number of medical ailments manifest themselves as defects in a patient's visual field. Patients suffering from, for example, macular degeneration, anterior ischemic optic neuropathy (AION), glaucoma, optic neuritis, detached retina, macular edema, central or branch retinal artery occlusion, some genetic impairments, and brain tumors may experience losses in visual acuity and visual field.
Non-invasive methods to measure a patient's visual field have been developed. For example, perimetry and campimetry provide information pertaining to the borderline between seeing and non-seeing areas within a patient's visual field.
Visual field tests employing visual field test patterns, such as an Amsler grid, have been developed to give a qualitative analysis of a patient's visual field. However such tests do not provide data of sufficient resolution or precision to perform a quantitative analysis of a patient's condition.
Recent developments of testing methods using visual field test patterns have included adjusting a patient's perception of the contrast levels within a visual field test pattern. For example, a method disclosed in U.S. Pat. No. 4,818,091, the disclosure of which is hereby incorporated by reference, requires the use of eyeglasses with polarized lenses to adjust the apparent contrast level of an Amsler grid.
These methods suffer from a variety of problems. Some methods require a patient to endure a long and boring testing process during which time the patient's concentration may lag because of fatigue. Other methods, while capable of being quickly performed, do not provide the spatial and contrast resolution required for high quality quantitative analysis.
Therefore, a need exists for a method that is quicker, simpler and more revealing than existing methods for characterizing the visual field. The present invention meets such need.